The invention relates to a tube connection between a collector of a motor vehicle heat exchanger and a line that feeds the inner heat exchange fluid to the collector or delivers it from the collector, having the further features according to the preamble of claim 1. Such a tube connection corresponds to the internal prior art of the Applicant Company.
The invention further relates to a novel method, having the features of claim 14, for the production of such a tube connection.
According to said internal prior art of the Applicant Company, it is customary to use an O-ring as a seal between a connecting sleeve on the collector and the line. Such an O-ring is firstly fitted onto the free end of the line and is then pressed with the latter into the wide cross section, remote from the collector, between the line and the connecting sleeve, in the ideal case with an outer flange of the connecting sleeve abutting against an outer bead of the line as the O-ring is pressed flat to the dimension of the wide cross section remote from the collector. In unfavorable cases, however, a section of the O-ring becomes partly caught in the intermediate space between the outer flange and the outer bead. This leads to premature damage to the O-ring, which in itself causes sealing problems because the actual sealing function of the O-ring becomes impaired. If the O-ring is not fitted optimally, or even merely because of its tolerances, it is not uncommon for sticking to actually occur when the connecting sleeve and the line are being slid together, merely because of the undesirably deformed O-ring, so that the tube connection does not always reliably take up its intended final position. This function is further compromised by the fact that the O-ring is intended to be guided on the inner surface of the connecting sleeve into the wide cross section remote from the collector, but the transition from this inner surface into the outer flange often has an unfavorable curvature, owing to tolerances, and the inner surface is further often modified by lateral spreading of a flux to such an extent as to impair the friction. When the O-ring is slid onto the free end of the line, it is also possible for the O-ring to suffer undesired twisting and turning, although in the ideal case it is supported from the rear of the outer bead. Such negative effects can only be overcome to some extent if a high fitting force is applied; however, this still leaves the risk of undesired deformation of the O-ring and of deformed regions of the O-ring entering the space between the outer bead and the outer flange. The difficulties of the known method are further exacerbated by the fact that, during the final assembly of the tube connection, the connection clips, which are customarily used for the final clamping of the outer flange and the outer bead together with the O-ring in between, can only be mounted, by gripping the outer flange and the outer bead, if the outer flange and the outer bead bear tightly on one another and are not forcibly spaced apart somewhat by extraneous inserted parts such as sections of the unintentionally deformed O-ring. This leads to a recognizable unsuccessful tube connection, which is discarded as a reject. But even if the outer flange and the outer bead do achieve the desired tight connection, this tight connection still always needs to be maintained using separate means while the connection clips are being mounted. In the case of manual assembly, as is customary in repair and servicing operations, for example, both hands are hence needed for mounting the clip, without for example having one hand still available to hold the tube or another aid, such as a pair of pliers or a lamp.
The object of the invention is hence to refine a tube connection of said type in such a way that it can be assembled easily and reliably, without the risk of incorrect connections, using only one hand or only one corresponding tool function, without having the tendency to come apart again by itself after assembly, but before a clamping device such as the connection clip etc. has yet been applied.
This object is achieved by all the features of claim 1.
As is shown particularly clearly by the preferred production method according to claim 14xe2x80x94with the expedient refinement according to claim 15, the two features of which are preferably both implementedxe2x80x94the seal according to the invention is not fitted into the connecting sleeve on the free end of the tube connection, like the O-ring previously was, but in the internal cross section, here the wide cross section remote from the collector, inside the connecting sleeve on the collector. This has the advantage that, with this pre-assembly, a rough surface on the inside of the connecting sleeve or an unfavorable curvature geometry existing there no longer represents a problem for fitting the seal, since the pre-assembly is carried out still without compression. In the final state of the tube connection, a part of the seal, namely its sealing flange, is then intentionally clamped between the outer flange of the connecting sleeve and the outer bead of the line.
Since seals of the type in question here, whether they are O-ring seals or the form of the seal according to the invention, are made from relatively pressure-resistant elastomer material, the final state of the tube connection can, even while accommodating tolerances, be set up accurately by abutment of the sealing flange between the outer flange and the outer bead on their surfaces that face one another. Since, in this case, at least one sealing element, which is equivalent in its sealing action to an O-ring of normal design, is formed on the insertion sleeve of the seal, no functional disadvantage compared with the conventional sealing by an O-ring has to be tolerated in the case of the tube connection according to the invention, and moreover all said disadvantages can be avoided. This is particularly important because, in terms of their industrial production, that is to say when they are mass-produced articles, tube connections of the type in question here are arranged relatively inaccessibly in the foot space of motor vehicles.
In particular, special emphasis should further be placed on the following advantages: because the sealing element, which acts in the invention in similar fashion to the previous O-ring, is arranged on the insertion sleeve, the sealing element can no longer twist its cross section in the circumferential direction, as results in the case of the conventional O-ring with the creation of shear forces, which in turn lead to premature ageing. During the final assembly of the tube connection, which can be carried out with relatively small axial assembly forces, these assembly forces are also particularly small because, when the free end of the line is being inserted into the insertion sleeve and optionally the narrow cross section of the connecting sleeve next to the collector, the insertion sleeve can expand axially and is hence deformable in the direction of travel during the insertion movement, without experiencing a transverse extension that creates resistance as in the case of the known O-ring. What is particularly important is that, as early as during the pre-assembly, the sealing element replacing the O-ring is arranged at its definitive sealing location in the widened cross section between the connecting sleeve and the free tube end, and does not need to be pressed into this widened cross section only during the final assembly. Lastly, the tube connection according to the invention is also more reliable in terms of the risk that the incorporation of a seal might perhaps be forgotten during assembly. In the previously known case in which an O-ring seal is used, omission of the latter may nevertheless still lead to temporary purely metallic sealing between the outer flange of the connecting sleeve and the outer bead of the line, although this temporary metal seal cannot withstand continuous operation. In the case of the tube connection according to the invention, the clamping device intended for the final clamping, for example a connection clip, is set from the start onto a sandwich-like succession of the outer flangxe2x80x94sealing flangexe2x80x94outer bead, and always leaves free a leakage gap acting as a leak between the outer flange and the outer bead, if the seal according to the invention is not incorporated.
In the case of the tube connection according to the invention, there are also other advantageous possible refinements according to the dependent claims. Some particularly important examples of these refinements will be emphasized below:
It is possible, according to requirements, to arrange further sealing elements on the insertion sleeve, on the sealing flange and in the transition region between the sealing flange and the insertion sleeve (cf. especially claims 6 and 7). In this context, distinction may be made between radially acting and axially acting sealing elements, and it is also possible to use both types.
Further, in addition to local sealing, it is also possible to provide extensive sealing (cf. especially claims 10 and 11). In the case of extensive pressure, however, it is necessary to take into account the fact that the components interacting with one another in each case have their own tolerances, so that extensive compression need not always be reliably ensured, and a capillary gap may possibly be created. So that this does not lead to more or less permanent leakage by capillary action, a capillary break is preferably also provided on the seal according to the invention in the vicinity of an extensive compression or even only a relative contact (cf. claim 12).
A wedge shape at the transition of the insertion sleeve into the sealing flange and/or a return projection engaging over the outer flange on the sealing flange (cf. claims 11 and 13), besides the fact that they further promote the sealing action, are also particularly helpful in avoiding the possibility that in the assembly, under particularly unfavorable circumstances, the insertion sleeve together with the sealing flange may be pressed into the wide cross section, remote from the collector, inside the connecting sleeve.
The invention will be explained in more detail below with reference to several illustrative embodiments, with the aid of diagrammatic drawings in which: